public class HomeWork08 {
	public static void main(String[] args){
		double num = 0;
		int flag = 1;
		int range = 100;
		int start = 1;
		for(int i = range;i <= range; i++){
			num += 1.0 / i * flag;
			flag = -flag;
		}
		System.out.println(num);
	}
}